HEV robust algorithms for magnetic speed sensor for engine applications

Abstract

Magnetic field sensors and sensing methods are provided. A magnetic sensor module is configured to measure a magnetic field whose magnitude oscillates between a first extrema and a second extrema. The magnetic sensor module includes a magnetic sensor configured to generate measurement values in response to sensing the magnetic field, and a sensor circuit. The sensor circuit is configured to generate a measurement signal based on the measurement values, compare the measurement signal to a switching threshold, generate a pulsed output signal having pulses that are generated based on the measurement signal crossing the switching threshold, measure a first characteristic of the measurement signal, update an offset of the switching threshold according to an offset update algorithm based on the measured first characteristic of the measurement signal, and selectively enable and disable the offset update algorithm based on at least a second characteristic of the measurement signal.

What is claimed is: 
     
       1. A magnetic sensor module configured to measure a magnetic field whose magnitude oscillates between a first extrema and a second extrema, the magnetic sensor module comprising:
 a magnetic sensor including a plurality of sensor elements configured to generate measurement values in response to sensing the magnetic field; and 
 a sensor circuit configured to:
 receive the measurement values from at least one of the plurality of sensor elements, and generate a measurement signal based on the measurement values received from the at least one of the plurality of sensor elements, 
 compare the measurement signal to a switching threshold, and generate a pulsed output signal having pulses that are generated based on the measurement signal crossing the switching threshold, 
 measure a first characteristic of the measurement signal and update an offset of the switching threshold according to an offset update algorithm based on the measured first characteristic of the measurement signal, and 
 selectively enable and disable the offset update algorithm based on at least a second characteristic of the measurement signal. 
 
 
     
     
       2. The magnetic sensor module of  claim 1 , wherein the first characteristic of the measurement signal is an average value of at least one first extrema of the measurement signal and at least one second extrema of the measurement signal. 
     
     
       3. The magnetic sensor module of  claim 2 , wherein the sensor circuit is configured to update the offset of the switching threshold by adjusting the offset to coincide with the average value. 
     
     
       4. The magnetic sensor module of  claim 1 , wherein:
 the second characteristic of the measurement signal is a frequency of the measurement signal, and 
 the sensor circuit is configured to measure the frequency of the measurement signal, compare the frequency of the measurement signal to a frequency threshold, and disable the offset update algorithm on a condition that the frequency of the measurement signal is less than the frequency threshold. 
 
     
     
       5. The magnetic sensor module of  claim 4 , wherein the sensor circuit is configured to enable the offset update algorithm on a condition that the frequency of the measurement signal is equal to or greater than the frequency threshold. 
     
     
       6. The magnetic sensor module of  claim 4 , wherein:
 the sensor circuit is configured detect a rotation direction of the magnetic field, count a number of consecutive pulses of the pulsed output signal that occur in a same rotation direction of the magnetic field, compare the number of consecutive pulses to a switching event threshold, and disable the offset update algorithm on a condition that the number of consecutive pulses is less than the switching event threshold. 
 
     
     
       7. The magnetic sensor module of  claim 6 , wherein:
 the sensor circuit is configured to enable the offset update algorithm on a condition that the frequency of the measurement signal is equal to or greater than the frequency threshold and on a condition that the number of consecutive pulses is equal to or greater than the switching event threshold. 
 
     
     
       8. The magnetic sensor module of  claim 1 , wherein:
 the second characteristic of the measurement signal is a number of consecutive extrema of the measurement signal that occur in a same rotation direction of the magnetic field, 
 wherein the sensor circuit is configured detect a rotation direction of the magnetic field, count the number of consecutive extrema of the measurement signal that occur in the same rotation direction of the magnetic field, compare the number of consecutive extrema to a switching event threshold, and disable the offset update algorithm on a condition that the number of consecutive extrema is less than the switching event threshold. 
 
     
     
       9. The magnetic sensor module of  claim 8 , wherein the sensor circuit is configured to enable the offset update algorithm on a condition that the number of consecutive extrema is equal to or greater than the switching event threshold. 
     
     
       10. The magnetic sensor module of  claim 1 , wherein:
 the sensor circuit includes a watchdog circuit that operates in parallel to a primary processing chain of the sensor circuit, the watchdog circuit being configured override a disabled state of the offset update algorithm set by the primary processing chain in order to re-enable the offset update algorithm, 
 the watchdog circuit being configured detect a rotation direction of the magnetic field, count a number of consecutive pulses of the pulsed output signal that occur in a same rotation direction of the magnetic field, compare the number of consecutive pulses to a switching event threshold, and re-enable the offset update algorithm when the number of consecutive pulses is equal to the switching event threshold. 
 
     
     
       11. The magnetic sensor module of  claim 1 , wherein the sensor circuit is configured to update the offset of the switching threshold thereby changing a value of the switching threshold according to the offset update algorithm and based on the measured first characteristic of the measurement signal. 
     
     
       12. The magnetic sensor module of  claim 11 , wherein:
 while the offset update algorithm is enabled, the sensor circuit is configured to periodically update the offset of the switching threshold thereby changing the value of the switching threshold, and 
 while the offset update algorithm is disabled, the sensor circuit is configured to maintain a current offset of the switching threshold thereby maintaining the value of the switching threshold. 
 
     
     
       13. The magnetic sensor module of  claim 12 , wherein:
 while the offset update algorithm is disabled, the sensor circuit is configured to maintain the current offset of the switching threshold thereby maintaining the value of the switching threshold regardless of the measured first characteristic of the measurement signal. 
 
     
     
       14. A method of measuring a magnetic field whose magnitude oscillates between a first extrema and a second extrema, the method comprising:
 generating a measurement signal representing the measured magnetic field; 
 comparing the measurement signal to a switching threshold; 
 generating a pulsed output signal having pulses that are generated based on the measurement signal crossing the switching threshold; 
 measure a first characteristic of the measurement signal; 
 updating an offset of the switching threshold according to an offset update algorithm based on the measured first characteristic of the measurement signal; and 
 selectively enabling and disabling the offset update algorithm based on at least a second characteristic of the measurement signal. 
 
     
     
       15. The method of  claim 14 , wherein the first characteristic of the measurement signal is an average value of at least one first extrema of the measurement signal and at least one second extrema of the measurement signal. 
     
     
       16. The method of  claim 15 , wherein updating the offset of the switching threshold includes updating the offset of the switching threshold by adjusting the offset to coincide with the average value. 
     
     
       17. The method of  claim 14 , wherein:
 the second characteristic of the measurement signal is a frequency of the measurement signal, the method further comprising: 
 measuring the frequency of the measurement signal; 
 comparing the frequency of the measurement signal to a frequency threshold; and 
 disabling the offset update algorithm on a condition that the frequency of the measurement signal is less than the frequency threshold. 
 
     
     
       18. The method of  claim 17 , further comprising:
 enabling the offset update algorithm on a condition that the frequency of the measurement signal is equal to or greater than the frequency threshold. 
 
     
     
       19. The method of  claim 17 , further comprising:
 detecting a rotation direction of the magnetic field; 
 counting a number of consecutive pulses of the pulsed output signal that occur in a same rotation direction of the magnetic field; 
 comparing the number of consecutive pulses to a switching event threshold; and 
 disabling the offset update algorithm on a condition that the number of consecutive pulses is less than the switching event threshold. 
 
     
     
       20. The method of  claim 19 , further comprising:
 enabling the offset update algorithm on a condition that the frequency of the measurement signal is equal to or greater than the frequency threshold and on a condition that the number of consecutive pulses is equal to or greater than the switching event threshold. 
 
     
     
       21. The method of  claim 14 , wherein:
 the second characteristic of the measurement signal is a number of consecutive extrema of the measurement signal that occur in a same rotation direction of the magnetic field, the method further comprising: 
 detecting a rotation direction of the magnetic field; 
 counting the number of consecutive extrema of the measurement signal that occur in the same rotation direction of the magnetic field; 
 comparing the number of consecutive extrema to a switching event threshold; and 
 disabling the offset update algorithm on a condition that the number of consecutive extrema is less than the switching event threshold. 
 
     
     
       22. The method of  claim 21 , further comprising:
 enabling the offset update algorithm on a condition that the number of consecutive extrema is equal to or greater than the switching event threshold. 
 
     
     
       23. The method of  claim 14 , further comprising:
 disabling the offset update algorithm by a primary processing chain; 
 operating a watchdog function in parallel to the primary processing chain; and 
 overriding a disabled state of the offset update algorithm set by a primary processing chain via the watchdog function to re-enable the offset update algorithm.